Glass fibre reinforced resin products are in wide use for many purposes. This form of synthetic plastic material is attractive from many points of view. It may be fabricated into attractive intricate shapes. It may be moulded in very large shapes. It has great inherent strength and durability, and is weather resistant. The uses of this type of fibre reinforced resin (FRP) products are too numerous to even mention. It is however well known that like many other manufacturing processes, it produces a significant degree of waste material, or reject articles. Waste material is produced in almost every case, by marginal portions or fringes of the material which extend around the edges of the mould and must be trimmed away. Some moulded articles are imperfect and must be rejected. Articles even of FRP, eventually are likely to wear out or become discarded.
In addition to all of these problems, the manufacture of the resins and of the glass fibre also results in wastage. The resins must be formulated strictly in accordance with specified formulations. Any quantities of resins which are "off spec" must be rejected as being unsaleable. The same is also true of the glass fibres themselves.
The very properties which make FRP an attractive material, also make it a serious problem from the point of view of disposal in an economical and above all ecologically satisfactory manner. Since the FRP material is highly resistant to weathering, if any quantities of it are placed in a dump it will remain there for many years, and will be virtually indestructible. Another of the properties of the FRP materials is their resistance to breaking and crushing. As a result, the disposal of waste FRP products presents a handling problem in that it is difficult if not impossible to crush them and compact them to a degree satisfactory for the waste disposal industry.
As a result of all of these problems, it is not unusual to find that the cost of disposal of waste FRP products is a significant item in the overall operating cost of the plant, both of the manufacturer of the base product and also the fabricators of the material.
At present there exists no market for waste FRP materials. Considerable experimentation has been conducted in certain countries in simply attempting to break down the material into some form of coarse, granular particles, in which form the waste FRP it can be easily handled and disposed of. However, in spite of very heavy expenditures, these experiments have not yet proven successful as a satisfactory method of disposing of such waste FRP materials.
It is of course apparent that even if such a line of experiments were successful all that would happen would be that the FRP waste materials would be dumped into the environment in a more concentrated form than is presently the case. So far as is known, no data exists as to the possible long term effects of the dumping of substantial quantities of highly concentrated FRP products, in this form, into the environment.
Other waste products are available which, while being less damaging to the environment, are nonetheless a problem from the aspect of simple disposal. Such products include waste materials such as concrete, glass, crushed stone, sand blasting materials, foundry slag, and the like.
Clearly, a more attractive solution to the problem would be to dispose of the waste FRP, and other waste products, in such a way that they were not simply dumped into the environment, but would be recycled into a useful material and in some way be reused on a more or less permanent basis.
Proposals have been made to grind FRP waste materials into a fine powder to be used as a filler in conventional sheet moulding compound (SMC). This fine powder was then intended to be mixed in the conventional manner with new resin and sandwiched between sheets of new reinforcing cloth to make SMC. This material remained in a semi-cured soft state until used. In use it was placed in a mould and subjected to high heat and pressure to mould thin sheet articles and to cure the partly cured resin.
This proposal required large proportions of fresh resins. Also the waste FRP powder contained catalysts. Some resins also the waste FRP powder contained catalysts. Some of these catalysts could react with the fresh resin and cause premature hardening of the material while stored in the semi-cured state. Consequently the shelf life of such sheet moulding compounds was uncertain and the results obtained in the end product were not reliable.